1. Field of the Invention
The present invention relates to a method and device for taking samples of liquids with different viscosities from a drum or other container.
2. Description of the Prior Art
Industry at large produces all kinds of liquid waste, in particular oils, hydrocarbons and chemical products. At present it is very difficult if not impossible to precisely define the proportions of the various constituents of the contents of a drum, especially if products with different densities and viscosities are mixed together.
At present, methods for identifying the content of a drum are somewhat erratic. They entail:
either inserting a dip-stick (a rigid rod or a metal wire) into the drum to extract thereon a product to be identified; this method is somewhat rudimentary and inaccurate; PA1 or, in a more effective method, taking samples by dipping a tube into the drum. When enough of the tube is immersed, the end remaining in the open is blocked off, the tube is rapidly extracted and the sample is collected in a flask. This method is irksome if samples are to be taken properly since it is essential to clean or to replace the tube before taking the next sample. PA1 a dip-tube, or columnar member, having a closure member at its lower end; PA1 a piston including at the end of a piston rod a disk or segment adapted to slide in the dip-tube, to which it is sealed; and PA1 means for temporarily positioning the piston disk in the heightwise direction so that this disk remains at a given distance from the surface of the fluid mass. PA1 the piston rod is part of a generally inverted U-shaped member of which one branch is constituted by the rod and another branch has at its lower end a bearing surface adapted to bear on a reference surface for the support ring, the branches being linked by the positioning means; PA1 the bearing surface is adapted to bear on the wall of the drum; PA1 the other branch is adapted to slide in a guide sleeve attached to the support ring at a distance from the passage; PA1 the sleeve includes a longitudinal slot and the other branch includes holding means projecting radially from the sleeve through the slot; PA1 the reference surface is linked to the support ring; PA1 the two branches of the U-shaped member are fastened together; PA1 the two branches of the U-shaped member are provided with means for adjusting their relative position; PA1 the other branch includes at its upper end a sleeve adapted to receive the piston rod which slides in it and is provided with clamping means; PA1 the support ring has on its lower face at least two annular centering steps matching at least two filler orifice diameters; PA1 the support ring includes an externally screwthreaded skirt; PA1 the dip-tube and the piston rod are provided with temporary fixing means; PA1 the aspiration end-piece includes a hole constituting an aspiration hole and a discharge hole; PA1 the hole has a diameter chosen according to the viscosity of the fluid mass to enable aspiration and discharge of the sample by relative disk/tube movement while preventing the sample from escaping under its own weight; PA1 the hole is formed in a split elastic seal and is flanked by one or more lips; PA1 the hole is closed by an anti-leak valve incorporating an opening member accessible from the outside; PA1 the discharge hole is in the wall of the tube near its upper end so that it is separated from the aspiration end-piece by the disk over only part of the relative sliding travel between the disk and the tube, a second piston disk provided with a non-return valve being provided in the tube under the disk to force discharge of the fluid sample by upward movement; and PA1 the second disk constitutes the aspiration end-piece.
However simple they might appear, these methods give only a vague idea of the content of the drum, especially if it contains mixed products with different viscosities. Syringes offer the advantage of much cleaner working conditions, but there remains the problem of sampling the constituents of the content of the drum in equal proportions. What is more, the use of syringes necessarily entails the use of a flexible hose which is soiled in each operation and therefore cannot be used for taking the next sample.
German Patent No. 4,211,633 discloses a sampling device including a piston in the form of a disk and a rod and a dip-tube inside which the cylinder can slide and to which it is sealed. A vertical rod is mounted at the side of the dip-tube and its lower end is fixed to a peripheral portion of a closure disk which, depending on the annular position of the rod about its longitudinal axis, exposes or closes off the lower end of the dip-tube. The enclosure has no top wall. In use, the piston rod (and thus the piston disk) is positioned relative to the enclosure (merely by suspending it, it would seem); by rotating the rod, the closure disk is offset to the side and the dip-tube is lowered to the bottom of the drum; the closure disk is then returned to the closure configuration. One drawback of this solution is that it allows only somewhat unreliable and somewhat impractical sampling of the content of the drum in the heightwise direction: when the dip-tube is lowered with the closure disk in the offset configuration there is a tendency for the tube to tilt away from a vertical configuration and the materials are strongly displaced from under the disk so that the liquid is stirred with the result that the liquid is seriously disturbed just when a reliable sample is required. The sampling device also necessarily pollutes all its exterior surfaces, which may require time-consuming and careful washing before each use. Less importantly, there is nothing to enable the taking of samples at different levels.
U.S. Pat. No. 3,115,782 concerns taking samples from a flow of liquid. It proposes a device including, disposed transversely to a flow pipe, a tube and a piston rod carrying at least two piston disks, one of which is an end disk. The tube is mounted in a retaining ring removably fixed to a transverse section of the pipe; the tube slides in and is sealed to the ring and the disks are adapted to slide in the tube, to which they are sealed. To take a sample the rod is moved across all of the section of the pipe until the end disk abuts against the inside wall opposite the transverse pipe. The flow is allowed to stabilize and then the tube is slid in the same way to trap a sample inside the tube (or a plurality of samples if there are more than two disks). The presence of the rod and the disk necessarily causes significant disturbance of the sample; further disturbances are caused by the lowering of the tube. It is important to note that this sampling device is intended for sampling a flowing liquid and that its use in a static mass would cause unacceptable disturbances during lowering of the rod and the disks to the bottom, as this would cause stirring throughout the volume through which the disks pass: taking a sample in this stirred volume would then yield results that would not be representative of the situation prior to stirring. Less importantly, this sampling device offers no adjustment of the height at which the sample is taken. As the sample is taken from on top of the terminal disk and around the rod, these parts are soiled as each sample is taken.
Note that all these prior art methods concern themselves very little with the risk of accidents or pollution connected with the manipulation of hazardous chemical products.
The invention proposes to remedy all these drawbacks by a method which aspirates and forces fluid into a vacuum chamber so that the fluid content (for example the static fluid content) of a drum or other container can be sampled simply and quickly, advantageously at a level that can vary, whether the fluid to be sampled is of liquid or paste-like consistency, without altering the proportions of the various constituents and with provision for scraping and cleaning parts in contact with the fluid so that successive samples of varied products can be taken without significant pollution of the drums or sample flasks by each other.